The probes are in response to a petition alleging the companies' 53-foot domestic dry containers are subsidised by the Chinese government and sold in the United States, both companies said in separate filings to the Hong Kong bourse on Monday.

The alleged dumping margin is 84.07 percent, they said, while Singamas added that the US authorities had estimated it was given a subsidy rate of at least 2 percent.

The containers transport goods other than bulk liquids within North America.

The US International Trade Commission is scheduled to make preliminary determinations on June 9, according to the filings.

Singamas said sales of 53-foot domestic dry containers amounted to $69.7 million, representing 5.4 percent of its total revenue in 2013, while CIMC said sales revenue from the US amounted to 640.4 million yuan ($102.74 million) in 2013, accounting for 1.1 percent of its total revenue.

Both companies said the probe was unlikely to have a major impact on their performance and financial position. They also said they were also seeking legal advice.

The investigations will take 12 to 18 months for completion, CIMC said.

In February, China urged the United States to "objectively and fairly" handle an ongoing trade dispute between the two countries after Washington signalled that it could extend import duties on Chinese solar panels to a wider range of products.